NFS: Allow walking nfs_client.cl_superblocks list outside client.c
We're about to move some fields from struct nfs_client to struct
nfs_server. There is a many-to-one relationship between nfs_servers
and nfs_clients. After these fields are moved to the nfs_server
struct, to visit all of the data in these fields that is owned by one
nfs_client, code will need to visit each nfs_server on the
cl_superblocks list for that nfs_client.
To serialize changes to the cl_superblocks list during these little
expeditions, protect the list with RCU.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4renewd.c b/fs/nfs/nfs4renewd.c
index 72b6c58..cde5650 100644
--- a/fs/nfs/nfs4renewd.c
+++ b/fs/nfs/nfs4renewd.c
@@ -63,9 +63,14 @@
ops = clp->cl_mvops->state_renewal_ops;
dprintk("%s: start\n", __func__);
- /* Are there any active superblocks? */
- if (list_empty(&clp->cl_superblocks))
+
+ rcu_read_lock();
+ if (list_empty(&clp->cl_superblocks)) {
+ rcu_read_unlock();
goto out;
+ }
+ rcu_read_unlock();
+
spin_lock(&clp->cl_lock);
lease = clp->cl_lease_time;
last = clp->cl_last_renewal;